ANALYTE SENSOR AND ITS MANUFACTURING

Abstract

This disclosure relates to an analyte sensor having a substrate, a working electrode, a second electrode and a membrane. The membrane is located on top of the second electrode. This disclosure further relates to a process for manufacturing the inventive analyte sensor as well as to an analyte sensor system having an analyte sensor according to this disclosure and an electronics unit. The analyte sensors according to this disclosure may be used for conducting an analyte measurement in a body fluid of a user.

Claims

1. An analyte sensor, comprising: a substrate having first and second sides; a working electrode positioned on the first side of the substrate, the working electrode comprising an electrically conductive material and an enzyme; a second electrode positioned on the second side of the substrate, the second electrode comprising silver; a membrane comprising a hydrophobic polymer, wherein the membrane is located on top of the second electrode, wherein the membrane comprises holes having a total area of at most 0.15 mm.sup.2.

2. The analyte sensor according to claim 1, wherein the analyte sensor is an implantable sensor.

3. The analyte sensor according to claim 1, wherein the second electrode is selected from the group consisting of a counter electrode, a reference electrode and a combined counter/reference electrode.

4. The analyte sensor according to claim 1, wherein the first and second sides of the substrate are positioned opposite each other.

5. The analyte sensor according to claim 1, wherein the second electrode comprises Ag/AgCl.

6. The analyte sensor according to claim 5, wherein the load of AgCl of the second electrode is in the range from 20 μg to 150 μg.

7. The analyte sensor according to claim 1, wherein the hydrophobic polymer comprises a hydrophobic thermoplastic polyurethane.

8. The analyte sensor according to claim 1, wherein the hydrophobic polymer has a glass transition temperature in the range from −100° C. to 0° C.

9. The analyte sensor according to claim 1, wherein the hydrophobic polymer has a water uptake of less than 1% by weight based on the total weight of the hydrophobic polymer.

10. The analyte sensor according to claim 1, wherein the working electrode is free of the membrane.

11. A method for manufacturing an analyte sensor, the method comprising: a) providing a raw substrate having a first side and a second side; b) preparing a working electrode region on the first side of the raw substrate, the preparing of the working electrode region comprising: b1) applying an electrically conductive material to the first side of the raw substrate, b2) applying a sensing material comprising at least one enzyme at least partially on the electrically conductive material, c) preparing a second electrode region on the second side of the raw substrate, the preparing of the second electrode region comprising: c1) applying a silver composition on the second side of the raw substrate, d) applying a hydrophobic polymer composition on top of the second electrode region to obtain a membrane; e) cutting the raw substrate comprising the working electrode region, the second electrode region and the membrane to obtain the analyte sensor.

12. The method according to claim 11, wherein the cutting in step e) comprises laser-cutting.

13. An analyte sensor formed by the method according to claim 11.

14. An analyte sensor system, comprising an analyte sensor according to claim 1 and an electronics unit configured to electronically connect to the analyte sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0171] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0172] FIG. 1 is a graph of normalized current versus time that shows experimental results.

DESCRIPTION

[0173] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

EXAMPLES

[0174] The following examples serve to illustrate this disclosure. They must not be interpreted as limiting with regard to the scope of protection.

[0175] For in vivo tests analyte sensors were prepared, the analyte sensors comprised the following:

substrate: PET, thickness of 130 μm
working electrode: [0176] electrically conductive material: layer of gold (100 nm thickness) with a layer of carbon paste on top [0177] enzyme: glucose oxidase comprised in sensing chemistry (Os-complex modified polymer)
second electrode: combined counter/reference electrode
electrically conductive material: layer of gold (100 nm thickness)
silver: Ag/AgCl paste

[0178] A membrane comprising a hydrophobic polymer (hydrophobic thermoplastic polyurethane) was located on top of the second electrode. The analyte sensors were laser cut. Holes were formed in the hydrophobic polymer of the analyte sensor depending on the laser cutting conditions of the cutting. A flux limiting membrane and a biocompatibility membrane covered the sensors.

[0179] Analyte sensors with the following total area of holes in the hydrophobic polymer were prepared: [0180] Sensor 1: 0 mm2 [0181] Sensor 2: 0.03 mm2 [0182] Sensor 3: 0.1 mm2 [0183] Sensor 4: 0.32 mm2

[0184] The analyte sensors were implanted in vivo in the same subject and the current measured over a period of eight days. In parallel regular blood glucose values (BG values) were measured with a BG meter using finger pricking. FIG. 1 shows the normalized current for the measurements with Sensor 2, Sensor 3 and Sensor 4. 0 on the x-axis shows the start of the measurement time after a run-in time of about 1 hour. The measurement curve for Sensor 1 is not shown as no current could be obtained.

[0185] Sensor 2 shows from the beginning of the measurement a sufficiently high current which remains constant throughout the whole measurement time (eight days). There are some peaks which indicate high and low glucose values during the measurement time. These peaks correspond to the peaks found in the regular blood glucose value measurements. Thus, the measurement with sensor 2 is particularly reliable and stable even over a longer time period. Further it allows calibration with the regular blood glucose value measurements.

[0186] Sensor 3 has a significantly longer run-in time, during which the current did not correlate with the BG values. It can be seen from FIG. 1 that the expected current is only reached after one day of measurement. Thereafter, the measurement is comparable in its reliability and stability with the one of sensor 2.

[0187] Sensor 4 exhibited an even longer run-in time, during which the current was significantly lower than expected. Though there are some peaks in the current visible, they did not correlate with the BG values and the sensitivity of the sensor (ratio of the current to the BG values) was too low and instable. After day seven, the current was significantly higher and correlated with the BG values and the sensitivity increased.

[0188] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.